Mine firing mechanism



April 14, 1959 J. B. GLENNON ET AL 2,881,702.

- MINE FIRING MECHANISM I Filed Aug. 9, 194; v 5 Sheets-Sheet 1Ei'li'llllllliiQ-Ffilllll" INVENTORS J.B. G NNON R.H. P K W.R. MALTBY BYc. HOBBS 9W ATTORNEY April 14, 1959 J. B. GLENNON ET AL 2,

MINE FIRING MECHANISM I Filed Aughs, 1941 I 5 Sheets-Sheet 2 .a. GLENNON.H. PARK W.R.MALTBY BY gmnoass ATTORNEY INVENTORS April 14, 1959 J. B.GLENNON ET AL 2,

. MINE FIRING MECHANISM Filed Aug. 9.;1941 s Sheets-Sheet 3 ATTORNEY J.B. GLENNON ET AL 2,881,702

April 14, 1959 I MINE FIRING MECHANISM 5 Sheets-Sheet 4 Filed Aug. 9,1941 INVENTORS J.B. GLENNON R.H. PARK W. C

R.MALTBY A. HOBBS ATTORNEY April 1959 J. B. GLENNON ET AL 2,881,702

MINE FIRING MECHANISM Filed Aug. 9. 1941 5 Sheets-Sheet 5 INVENTORS B.GLENNON .H. PARK MALTBY H 03 B 3 BY W ATTORNEY J. R W

United States Patent 2,881,702 MINE FIRING MECHANISM James B. llennon,Washington, 1).c., Robert H. Park, Pluckemm, N .J., Wilson R. Maltby,Washington, D.'C., and Charles A. Hobbs, Atlanta, Ga.

Application August 9, 1941, Serial No. 406,236 36 Claims. Cl. 102-18)(Granted under Title 35, US. Code (1952), sec. 266) instrument in whichthe field continues to change over a predetermined period of time andcontrolling the firing .of the mine in accordance with the changingnature of the magnetic field detected by the device.

In devices of this character heretofore proposed in which a changingmagnetic field is employed for firing a submarine mine, it has beenfound that an impulse of heavy current applied to an electricalconductor attached to a vessel moving within the vicinity of the mineand insulated from the sea water within which it is immersed except atthe furthermost end thereof, causes a magnetic field to be set up withinthe water about the conductor of sufficient intensity to cause the mineto explode. This method of detonating a mine is referred to herein asmine sweeping, the electrical conductor employed for this purpose isalso referred to herein as a sweep wire, and the vessel as a minesweeper. Thus with the types of submarine mines heretofore devisedemploying firing mechanisms controlled by changes in the terrestrialmagnetic field, a mine field may be swept and the mines thereofdetonated by a mine sweeper systematically cruising over the field andapplying current impulses at periodic intervals of time to a sweep wiretrailing from the vessel.

In order to establish an effective magnetic field of considerable sizeabout the sweep wire, it has heretofore been foundnecessary to employ anelectric current of such strength that the source of electrical energyis only sufiicient to. allow the current to be applied to the sweep wireperiodically for short periods of time.

In the system of the present invention the mine firing mechanismincludes certain selecting and time delay elements in combination withthe field sensing device whereby the detonation 'of the mine is effectedonly when the magnetic'field continues to change for a predeterminedperiod of time such, for example, as the continuing change of magneticfield caused by the movement of a steel vessel or any vessel having aconsiderable amount of magnetic material therein past the mine disposedadjacent the path of travel of the vessel. By reason of the selectingand time delay elements and circuit connections therebetween thedetonation of the mine by a mine sweeping operation of the type referredto hereinbefore is highly improbable.

Furthermore, the mine is rendered absolutely safe for transportation andhandling and assumes an armed condition only after being launched byreason of the provision of certain safety control devices and circuitstherefor, the operation of which will become more clear- 1y apparent asthe description proceeds. In the event that the mine should fail tobecome armed within a prede- 2,881,702 Patented Apr. l4, 1959 2 terminedtime after being launched, or if the mine should be raised from the bedof the body of water within which it had been planted to a predetermineddepth beneath the surface of the water, means are provided forautomatically causing the mine to be exploded.

One of the objects of the present invention is toprovide a new andimproved magnetic influence mine firing mechanism, selectivelyresponsive to a changing magnetic field, of simple and ruggedconstruction which will be economical to manufacture and possess thedesired qualities of reliability and eificiency in use and operation.

Another object is to provide a mine firing device of the above generalcharacter having new and improved means for sensing changes in themagnetic field adjacent the device periodically during a predeterminedperiod of time and detonating the mine when the changing magnetic fieldhas continued during the predetermined period of time.

Another of the objects resides in the provision of new and improvedmeans responsive to a changing magnetic field for firing a submarinemine in proximate amidship relation to a vessel moving past the mine.

Another of the objects resides in means in which different portions of aships magnetic signature are employed in succession for firing asubmarine mine.

Another object is the provision of means for arming a submarine mineunder control of a predetermined number of vessels moving past the mine.

Another object is the provision of means responsive to a changingmagnetic field for comparing the continuance of a changing magneticfield with a plurality of predetermined intervals of time andselectively firing an explosive in accordance with the results of suchcomparison.

Another of the objects resides in the provision of means responsive to achanging magnetic field for storing indications representing changingconditions of the field at intervals and controlling the operation of adetonating device in accordance with the indications stored.

Another of the objects is the provision of new and improved meansresponsive to the launchingv of the mine within a body of water forautomatically resetting a 'signal storing device adapted to besubsequently controlled by a changing magnetic field.

A further object is the provision of means for storing a plurality ofindications of changes in a magnetic field received at predeterminedintervals of time and restoring the storing means to a predeterminedcondition when any of the changing indications are not received, inregular order within a predetermined period of time. d

A further object is the provision of a system vhaving means for causinga mine firing mechanism to perform a test cycle of operations as the"mineis launched and either to arm or destroy the mine in accordance withthe result of the test. H 1

A still further object resides in the provision 'of' new and improvedmeans for causingthe destruction of a submarine mine in response tomovement of the mine toward the surface of the body of water withinwhich the mine is planted.

Still further objects, improvements and advantages will be apparent fromthe following detailed description, taken in connection with theaccompanying drawings, of which:

Fig. 1 is a view partly in section of a submarine mine employing thesystem of the present invention;

Fig. 2 is a view somewhat enlarged taken substantially along the line 22of Fig. 1 showing the extender hydrostat and contacts controlledthereby;

Fig. 3 is a view taken along the line 3-3 of Fig. 2;

Fig. 4 is a view in perspective of the firing control mechanism of Fig.1 withthecover removed;

detected by the device of Fig. 4;

Fig. taken in connection with Fig.8, illustrates graphically thevariations in a magneticfield caused by the passage of each of twoundegaussed vessels of different sizepast a point of reference; I

Fig. it) taken in connection with Fig 8, illustrates graphically thevariations ina magnetic field caused by the passage of each of twodegaussed vessels of different size past point of reference; and I Fig.11 illustrates in diagrammatic form the entire s st m- Referring firstto Fig. 1 of the drawings there is shown thereon a submarine mineindicated generally by the numeral 1 within which is disposed a fieldchanging detection mechanism comprising an induction or search coil 2connected as by the cable 3 to a mine firing control unit 4 operativelyconnected to a detonator 5 The mine is provided with a suitable aperture6 within which is disposed a hydrostat 7 in sealed relation to thecasing of the mine adapted to extend the detonator within the explosivebooster charge 8 contained within the compartment 9. An explosive charge11 surrounds the compartnient Q and completely fills the explosivechamber 12. The mine is also provided preferably with a plurality offins 13 by means of which the mine is directed along apredetermined lineof flight as to the mine is launched. A soluble washer 14 is providedwithin the aperture 6 for preventing the operation of the extenderhydrostat for a predetermined period of time after the mine has beenlaunched; u

The extender hydrostat comprises a flexible diaphragm 15, Fig. 2,securely held in position at the outer edge thereof as by the retainingring 16 and bolts 17. The diaphragm is normally held in an outwardposition by a spring 18 acting against a shoulder 19 secured to theshaft 20in any suitable manner as by brazing the parts together. Adetonator 21 is secured to the shaft 20 as by the screws 22. The casingof the mine is provided with "an extended portion 23 within which theshaft 20 is adapted to move. Secured to the plunger as by the screw 24is a cam member 25 of insulating material suitable for the purpose such,for example, as Bakelite, hard rubber, fiber or the like having camsurfaces adapted to engage the contact springs 26 and 27 and move theminto engagement with the contact springs 28 and 29 respectively as thehydrostat is operated by the pressure of the water within "which themine is immersed. The cam member '25 is provided with a slotted camportion 31 adapted to be engaged by the cam follower 32 secured to theend of the contact spring 33 and adapted to move the contact spring intoengagement with the contact spring 34 in the event that the shaft '20 isreturned to its flannel position by the spring 18 as the mine is raisedto a predetermineddepth beneath the surface of the body of water withinwhich the mine is laid. The contact springs 26, 27, 28, 29, 33 and 34are electrically insulated from each other and from the casing of themine as by the insulating bus'hings 35, and securely clamped in V theassembled position as by the screws 36, a projecting boss 30 beingprovided on the extended portion 23 to support the "contact springs 33and 34. In order that the description of the operation of the system maybe facilitated, the contactsprings 26 and 28 are hereinafter referred toas contact 1, springs 27 and 29 as contact 2,

and 33 and 34 as contact 3. A soluble washer 14 having a suitableaperture therein adapted to receive the shaft 20and secured thereto asby the nuts 40 is disposed within the aperture 6 in abutting relationwith a shoulder 4 37 whereby movement of the hydrostat shaft isprevented until the soluble washer has become dissolved or softenedsufliciently to permit movement of the shaft. The soluble washer may becomposed of any material suitable for the purpose such, for example, assalt, glycerin, sugar and glue or similar ingredients.

The control mechanism of Fig. 4 comprises the mounting plates 38, 39,and 41 held together in spaced relation as by the studs 42 and nuts 43,the plate 41 forming a base having a plurality of lugs 44 securedthereto in any suitable manner as by welding or brazing the partstogether. Each of the lugs is provided with a tapped hole adapted toreceive a screw or bolt whereby a suitable enclosing cover 50, Fig. 5,may be secured thereto. A pad 47, Fig. 1, of resilient material suitablefor the purpose, such, for example, as sponge rubber is provided forengaging the cover 50 and yieldably supporting the control mechanismwithin the mine casing. The plate 41 is provided preferably with formedportions or tabs 45 adapted to secure a battery 46 in clamped positionbetween the plates 39 and 41 or, if desired, the battery 46 may bemounted within a suitable compartment and yieldably insulated therefromby the pad or cushion 10 in the manner indicated on Fig. 1.

A sensitive control relay 48 such, for example, as the relay known inthe trade as a sensitrol relay, is mounted within a resilient cushionmounting 51 of material suitable for the purpose such, for example, asrubber secured to the plate 38 as by the mounting ring 52 and screws 53,Figs. 4 and 6. A relay 54 is secured to the plate 38 as by the mountingstuds 55 and provided with terminals 56 for external electricalconnection. A selection switch SS is also mounted on the plate 38 andsettable to different positions in accordance with the number of shipswhich may be allowed to pass the mine in succession before the mine isdetonated. Three switches designated T81, T82, and T53, are provided forchanging the number of successive operations of the detecting mechanismrequired to complete a cycle of operations thereof. A terminal strip 57is secured to the plate 38 as by the screws 58 and provided with aplurality of terminals 59 electrically connected to the unit by theconductors 61. A cable 62 comprising a plurality of electricalconductors 63 connected at one end thereof to the terminals 59 isemployed for establishing a circuit connection between the control unitand the extender hydrostat. The cover 50 is provided preferably with abushing 60 of suitable insulating material having an aperture thereinadapted to receive the cable 62.

On Fig. 7 is shown the plate 39 on which is mounted a time delay relayTD2 comprising an electrically oper ated clock mechanism having a pairof electrical contacts adapted to be closed in response to engagement bythe arm 80 preferably of insulating material within a predeterminedinterval of time such, for example, as nine seconds after electricalenergy is first applied to the relay mechanism. A second time delayrelay TD4 comprising clock mechanism is also attached to the plate 39,the mechanism comprising a pair of electrical contacts 81 adapted to beclosed in response to engagement by the arm with a delay ofapproximately two seconds as the operate circuit to the electricalWinding mechanism of the relay is interrupted. Each of the delaymechanisms TDZ and TD4 is provided with a resilient mounting 64 ofrubber or similar material held to the mounting plate 39 as by themounting ring 65 and screws 66. A selector switch A having two terminalbanks adapted to be engaged by wipers is also attached to the plate 39,and a selector switch B having a single termi nal bank is also securedto the plate.

Fig. 8 shows a typical vessel having a preponderance of magneticmaterial distributed unequally throughout the vessel and adapted toinfluence the earths magnetic field in varying degrees as dilferentportions of the vessel move past a fixed point of reference. Themagnetic field adjacentthe point of reference or observation is thusvaried or changed and the direction of the field is also changed inaccordance with that portion of the vessel moving past the referencepoint. Stated differently, each portion of the vessel may be regarded asexerting a magnetic influence upon the terrestrial magnetic field ofvarying degree whereby the influence of the terrestrial magnetic fieldis increased or decreased by the presence of the vessel, as the case maybe. A steel vessel, for example, may acquire a certain degree ofmagnetism imparted thereto during the process of fabrication of thevessel and may additionally acquire magnetic properties by reason of themovement of the vessel in the earths magnetic field, and thus a steelvessel casts a particular magnetic shadow or zone of magnetic influenceabout the vessel in accordance with a particular pattern referred toherein as a ships signature.

Referring now to Fig. 9 and more particularly to curve A thereof inwhich the signature of a ship such as the ship of Fig. 8 is illustrated,the various portions of the curve A correspond generally to the adjacentportions of the vessel. The dashed line H extending across the figureindicates the earths magnetic field at the latitude corresponding to thepath of travel of the vessel and the numerals 10, 20, and 25 appearingdirectly below the dashed line indicate the interval of elapsed time inseconds since the bow of the vessel passed the point of reference. Themagnetic field represented by the curve A, it will be noted, isdecreased slightly ahead of the bow of the vessel and increased as thevessel moves along a point of reference until the central portion of thevessel is opposite the reference point, thereafter decreasing to theinitial strength of terrestrial field as the vessel continues itsmovement past the reference point, the variation in the strength of themagnetic field being discontinued shortly after the stern of the vesselpasses the point of reference.

The curve A may be regarded as the signature of a small undegaussedvessel moving at a relatively slow rate of speed and the curve B as thesignature of a larger vessel moving at a higher rate of speed wherebythe same interval of time is required for each of the vessels to passthe point of reference. The curve B, it will be noted, is generallysimilar to the curve A but represents a greater change in the earthsmagnetic field caused by the passage of the larger vessel than thechange represented by the curve A.

The curve C, Fig. 10, illustrates by way of example, the magneticsignatureof a degaussed vessel such, for example, as the vessel of Fig.8 in which, by reason of the disposition of the magnetic materialthroughout the vessel and the method employed for degaussing the same,the magnetic field of the ship is caused to make several reversals asthe ship passes the point of reference, there being six such reversalsof the field in the ships signature represented by the curve C. -It willalso be noted that the intensity of the magnetic field is varied from apositive to a negative value with respect to the earths magnetic fieldindicated by the letter H such that a substantially symmetrical curve isproduced about the dashed line H attenuating somewhat as the stern ofthe vessel approaches the point of reference. The curve C may beregarded as the magnetic signature of the vessel corresponding to thecurve A when the vessel is in a degaussed condition. In a similar mannerthe curve D, Fig. 10, may be regarded as the signature of the vessel ofthe curve B when in a degaussed condition, the degaussed vessel passingthe point of reference during the same time interval as the vessel ofcurve C.

The manner in which the signature of a vessel, whether degaussed orundegaussed, is employed during a plurality of intervals of time forselectively firing a submarine mine as the vessel moves past the minewill now be described.

The operation of the system of the present invention shown on Fig. 11will best be understood by consideration of a specific illustration.Assume, by way of example, that a;soluble plug 14 has been placed inoperative position within the aperture 6, and that the selector switchesA and B have been set to their normal or initial positions with thewipers of switch A in engagement with contact 1 of their respectiveswitch banks, ,the wiper of switch B in the position shown on Fig. 11,switch SS has been set to position 1, switches T82 and T83 are operated,switch T81 is unoperated, and the mine has been launched in a body ofwater of depth sufficient to cause the extender hydrostat to operate.

Upon striking the water the mine sinks .and comes to rest on the bed ofthe body of water and, after a predetermined period of time, the solubleplug dissolves or is softened sufiiciently to allow the extenderhydrostat to be operated by the pressure of the water. As the hydro statis moved from its initial position, contact 1 closes momentarily andcompletes a circuit from positive terminal of battery BA, conductor 67,winding of the reset magnet RS-A of the switch A, conductor 68, contact1 of the extender hydrostat, conductor 69 and thence to the negativeterminal of battery BA thereby causing the reset magnet RS-A to operateand restore the wipers of the switch A to their normal or initialposition in engagement with terminal 1 of their respective switch banksin the event that the wipers have been moved from their initial or homeposition prior to the launching of the mine or as the result of theviolent shock received when the mine was launched. As the extenderhydrostat continues its movement, contact 1 opens therebyinterruptingthe operate circuit to the winding of the reset magnet RS-Aand causing the reset magnet to release. As the hydrostat continues itsmovement contact 2 closes and remains closed during the life of themine.

A test cycle of operation is now made as follows. Relay TD2 operatesover the following circuit: Positive pole of battery BA, conductor 67,winding of relay TD2, conductor 70, wiper 1 and terminal 1 of switch A,conductor 74, contact 2, conductor 69 and thence to the negative pole ofbattery BA. Relay TD2 is a time delay relay arranged to close itscontacts after a predetermined period of time such, for example, as nineseconds after an operate circuit has been completed to the windingthereof. Relay D operates over the following circuit: Positive terminalof battery BA, conductor 67, high resistance 71, winding of relay D inparallel with the search coil SC, high resistance 72, conductor 73,terminal 1 and wiper 2 of switch A, conductor 74, contact 2, conductor69, and thence to the negative terminal of battery BA. The operation ofrelay D at its armature closes a circuit from positive terminal ofbattery BA, conductor 67, armature 75 and make contact 76 of relay D,conductor 77, winding of relay P, conduct0r 74, contact 2, condoctor 69and thence to negative battery, thereby causing relay P to operate. Asarmature 78 of relay P moves into engagement with its make contact, acircuit is closed from positive battery BA by way of conductor 67,winding of time delay relay TD4 in parallel with the stepping magnetSTP-B of switch B, conductor 79, make contact and armature 78 of relayP, conductor 74, contact 2, conductor 69 and thence to negative battery,thereby causing the operation of the time delay relay TD4 and thestepping magnet STP-B. The operation of relay TD4 causes the armature 81thereof to move into engagement with its make contact and there toremain for a period of time such, for example, as three seconds afterthe operate circuit to the winding of relay TD4 has first beencompleted. As armature 81 of relay TD4 moves into engagement with itsmake contact, positive battery is applied to conductor 82, winding ofreset magnet DR I of relay D from whence the circuit is continued by wayof conductor 74, contact 2, conductor 69, and thence to negative batterythereby causing the reset magnet DR-to operate and restore. the armature75 of relayv D to -a position intermediate the contacts 76 and 83regardless of the energized condition of the operate magnet of relay D.

The operation of stepping magnet STP-B causes the switch wiper thereofto be moved into engagement with terminal 1. As the wiper of switch Bmoves from its initial or rest position, contacts ON-B are closed.

As armature 75 of relay D is disengaged from its contact 76, the operatecircuit to relay P is interrupted. Relay P is a slow releasing relay byreason of a copper slug encircling the core of the operate magnetthereof and for this reason does not release until approximatelythree-tenths'of a second after the circuit to the relay winding has beeninterrupted. As armature 78 of relay P moves out of engagement with itsmake contact, negative battery is removed from conductor 79 therebydeenergizing the operate winding of relay TD4 and the stepping magnetSTP-B. The stepping magnet STP-B releases but, as heretofore stated,armature 81 of relay TD4 does not move out of engagement, with its makecontact until three seconds after the winding of relay TD4 wasdeenergized. At the completion of the three second period hereinbeforereferred to, armature 81 of relay TD4 moves away from its make contactthereby removing positive battery from conductor 82 and causing thereset magnet DR of relay D to release, whereby the armature 75 of relayD is free to respond to a signal received by the operate winding ofrelay D.

As the wiper 2 of switch A is still resting on its terminal 1 at thistime, negative battery is applied to conductor 73, resistance 72 and theoperate magnet of relay D remains energized, thereby causing armature 75of relay D to be again moved into engagement with its contact 76. Whenthis occurs, relay P operates and applies negative battery to conductor79 thereby causing the operation of relay TD4 and the stepping magnetSTP-B. The operation of the stepping magnet causes the wiper of switch Bto be moved into engagement with its terminal 2. The operation of relayTD4 causes the reset magnet DR to operate and restore the armature 75 ofrelay D to its intermediate position. As armature 75 of relay D movesaway from its contact 76 the operate circuit to relay P is interruptedand, after a delay of three-tenths of a second, relay P releases and atits armature 78 interrupts the circuit to relay TD4 and the steppingmagnet STP-B. As armature 81 of relay TD4 moves away from its makecontact, positive battery is removed from conductor 82 thereby releasingthe reset magnet DR and allowing the armature 75 to be again broughtunder control of the operate magnet D.

As the operate magnet of relay D is still energized at this time,armature 75 again moves into engagement with its contact 76 therebycausing relay P to operate and, at its armature 78 and make contactthereof, apply negative battery to relay TD4 and the stepping magnetSTP-B thereby causing relay TD4 to operate and the stepping magnet STP-Bto advancethe wiper of switch B into engagement with its terminal 3. Acircuit is now completed from positive battery, conductor 67, winding ofstepping magnet STP-A, conductor 84, contacts of switch TS3, contacts ofswitch TSZ, terminal 3 and wiper of switch B, conductor 74, contact 2,conductor 69 and thence to negative battery thereby causing the steppingmagnet STP-A to operate and advance the wipers of switch A ahead totheir terminals 2. The operation of relay TD4 at its armature 81 andmake contact thereof,

1 causes the reset magnet DR of the switch D to restore the armature 75thereof to its neutral position between the contacts 76 and 83 therebycausing relay P to release. The release of relay P removes negativebattery from conductor 79 thereby releasing the stepping magnet STP-Band deenergizing the time delay relay TD4. As armature 81 of relay TD4moves away from its make contact, positive battery is removed from thereset magnet DR thereby removing the restraint from armature 75 of relayD whereby the armature is free to respond to subsequent signals receivedby the operate winding of relay D. As wiper 2 of switch A moves out ofengagement with its terminal 1, negative battery is removed fromconductor 73 thereby deenergizing the operate magnet of relay D, andrendering the relay responsive to changes in the magnetic field detectedby the search coil SC. As wiper 1 of switch A moves off terminal 1 ofits switch bank, the operate circuit to relay TD2 is interrupted but,regardless of this circuit interruption, the clock mechanism of relayTD2 continues to function until armature thereof engages the makecontact. The wiper of switch B, it will be recalled, is now resting onits terminal 3, and the Wipers of switch A on their terminals 2.

Shortly after the foregoing cycle of operations has been completed andat the end of the nine second period following the completion of theoperate circuit to the winding of relay TD2, armature 85 of relay TD2engages its make contact momentarily thereby applying negative batteryby way of conductor 86 to the winding of the reset magnet RS-B of switchB, the circuit continuing by way of conductor 67 to positive batterythereby causing the reset magnet RS-B to operate and restore the wiperof the switch B to its normal position. As armature 85 is disengagedfrom its contact, reset magnet RS-B releases. The test cycle ofoperation is now complete, and the mineis in a condition to respond to achange in the magnetic field adjacent the mine.

The operation of the system in response to a change in the magneticfield caused by a mine sweeping operation will now be described. Assume,by way of example, that an impulse is received from a sweep Wire by thesearch coil SC of sufficient magnitude and duration to cause thearmature 75 of relay D to be moved into engagement with one of itscontacts as, for example, the contact 76. Positive battery at armature75 of relay D is applied by way of contact 76 to conductor 77 therebycausing relay P to operate. As armature 78 of relay P moves intoengagement with its make contact, negative battery is applied toconductor 79 thereby causing relay TD4 and the stepping magnet STP-B tooperate. The operation of the stepping magnet STP-B causes the wiper ofswitch B to be moved into engagement with terminal 1 of the switch bankand the off-normal switch contacts ON-B to close. A circuit is nowcompleted from positive battery, conductor 67, winding of relay TD2,conductor 70, wiper 1 and terminal 2 of switch A, conductor 87, contactsON-B, conductor 74, contact 2 of the extender hydrostat, conductor 69,and thence to negative battery thereby causing relay TD2 to operate andclose its contacts nine seconds later. The operation of relay TD4 at itsarmature 81 and make contact thereof causes the reset magnet DR of relayD to operate and reset the armature 75 thereof. As armature 75 of relayD moves away from contact 76 the operate circuit to relay P isinterrupted and relay P releases. The release of relay P at its armature78 causes the release of the stepping magnet STP-B and thedeenergization of the operate magnet of the time delay relay TD4.Armature 81 of relay TD4, it will be recalled, does not becomedisengaged from its make contact until a period of three seconds haselapsed following the energization of the operate winding thereof. Whenthis occurs, positive battery is removed from one end of the winding ofthe reset magnet DR, thereby removing the restraint from armature 75 ofrelay D and allowingthe relay to respond to a subsequent signal receivedfrom the search coil SC generated by the search coil in response to achanging magnetic field. The wipers of switch A are now resting on theirterminals 2, and the wiper of switch B on its terminal 1.

If a second impulse should now be received from the sweep Wire such, forexample, as would be caused by an interruption or reversal of thecurrent flowing within the sweep wire, an electromotive force ofopposite polarity would be generated within the search coil SC and suchan impulse might be of sufficient intensity and duration to causearmature 75 of relay D to. be moved'into engagement with contact 83.Should this occur, positive battery at armature 75 of relay D is appliedby way of contact 83 and conductor 77 to one end of the winding of relayP, thereby causing relay P to operate and at its armature 78 applynegative battery to relayTD4 and the stepping magnet STP-B. Theoperation of the stepping magnet STP-B advances the wiper of switch Binto contact with terminal 2 of the switch bank. The operation of relayTD4 causes the reset magnet DR .to operate and restore the armature 75of relay D to its neutral or intermediate position three seconds afterthe operate circuit of relay TD4 has been completed. As armature 75 ofrelay D moves away from contact 83, relay P releases thereby removingnegative battery from conductor 79 and cansing relay TD4 and thestepping magnet STP-B to release. A time interval of approximately sevenseconds has now elapsed since a change in the magnetic field was firstdetected by the search coil SC and, as is the general practice in minesweeping operations at present employed, no further impulses will betransmitted by the sweep wire during the three second intervalimmediately following the release of the reset magnet DR.

At the completion of the nine second interval of time following thefirst operation of relay D in response to an impulse set up by a sweepoperation, armature 85 of relay TD2 is moved into momentary engagementwith its make contact thereby applying negative battery by way ofconductor 86 to the reset magnet RS-B of switch B and causing the wiperof switch B to be'restored to its home or initial position and theswitch contacts ON-B to open. The mine is now restored to its originalpartially armed condition.

In the event that a single impulse only is received from the sweep wirethe wiper of switch B is stepped ahead to terminal 1 as relay P operatesand remains on terminal 1 until armature 85 of relay TD2 engages itsmake contact after a time delay of nine seconds, thereby operating thereset magnet RS-B and restoring the switch wiper to its normal orinitial position.

The operation of the mine in response to a changing magnetic fieldcaused by a moving ship will now be described. Let it be assumed,by wayof example, that an undegaussed ship having a magnetic signature such asshown by curve A, Fig. 9, is approaching a mine planted adjacent thepath of travel of the vessel, at a rate of speed such that the timerequired for the vessel to travel a distance equal to the length of thevessel is substantially 25 seconds. As the bow of the vessel moves pastthe mine the intensity of the magnetic field adjacent the mine isincreased, thereby causing "an electromotive force to be generated bythe search coil 2, hereinafter referred to as SC, of sufficientmagnitude to cause movement of the armature 75 of relay D from itsneutral position, this movement of the armature occurring during thatportion of the curve A indicated by the letter X. The movement ofarmature 75 continues until it is arrested by engagement with contact76, the point on the curve A at which this occurs being indicated by thenumeral 88, Fig. 9. The vessel at this time will have moved through adistance M and the magnetic field will be changed by an amount N duringthe time required to operate relay The operation of relay D, Fig. 11,causes relay P to operate and apply negative battery to the steppingmagnet STP-B and the time delay relay TD4. The stepping magnet operatesand advances the wiper of switch B to terminal 1 of the switch bank.Relay TD4 operates and at its armature 81 causes the operation of thereset magnet DR which forcibly restores the armature 75 of relay D to aneutral position intermediate the contacts 76 and 83 and maintains thearmature in a neutral position until the reset magnet is released.As-armature 75 is disengaged from contact 76 the operate circuit torelay P is interrupted and relay P releases after a delay of threetenthsof .a second, thereby interrupting the operate circuit to the steppingmagnet STP-B and the time delay relay TD4. Relay TD4, it will berecalled, releases after a three second delay thereby removing positivebattery from one end of the winding of reset magnet DR. ,The resetmagnet DR releases thereby removing the restraint from armature 75 ofrelay D and permitting the detector relay D to respond selectively to asubsequent signal re ceived from the search coil SC.

The point on the magnetic curve A at which restraint is removed fromarmature 75 of relay D is indicated by the numeral 89 and the ship, itwill be noted, has advanced a fractional part of its length since thefirst change in the magnetic field was detected by the search coil SC.The continued movement of the ship past the mine causes the magneticfield sensed by the search coil at 89 to be increased untilthat portionof the vessel corresponding to the point 91 on the curve A is oppositethe mine, at which time relay D again closes its contacts by reason ofan increase in the intensity of the magnetic field indicated by theletter O for a period of time represented by the letter R. As armature75 again moves into engagement with contact 76 the cycle of operationsjust described is repeated and the wiper of switch B is moved intoengagement with terminal 2 of the switch bank. As armature 81 of relayTD4 engages its make contact, the reset magnet DR operates and restoresarmature 75 of relay D to its neutral position and prevents furthermovement of the armature therefrom until the reset magnet DR releases.After a three second delay armature 81 of relay TD4 moves away from itsmake contact thereby releasing the reset magnet DR and permittingmovement of the armature 75. By this time the vessel will have movedahead until that portion of the vessel corresponding to the point 92 ofthe curve A representing the magnetic signature of the vessel isopposite the mine. Continued movement of the vessel causes the magneticfield to be changed until the point 93 of the curve A is reached, theship having moved ahead a distance from the point 92 by an amount S andthe magnetic field having changed by an amount T, at which time armature75 of relay D again engages contact 76. An interval of approximatelyeight seconds has now elapsed since relay D was first operated by thechange in magnetic field caused by the movement of the ship, duringwhich time the ship has moved ahead sufficiently to bring the centralportion thereof opposite the mine.

The operation of relay D in response to the increase T of the magneticfield causes relay P to operate, and at its armature 78 apply negativebattery to conductor 79 thereby operating relay TD4 and the steppingmagnet STP-B. The operation of stepping magnet STP-B causes the wiper ofswitch B to be moved into engagement with contact 3 of the switch bank.A circuit is now completed from positive battery BA, conductor 67,winding of stepping magnet STP-A, conductor 84, contacts of switches T83and T82, terminal 3 andwiper of switch B, conductor 74, contact 2 of theextender hydrostat, conductor 69 and thence to negative battery therebycausing the stepping magnet STB-A to operate and advance the wipers ofswitch A to position 3.

a of the settable switch SS having a wiper 94 adapted to engage thecontacts selectively in accordance with the set position of the switch.The wiper 94 is connected by the conductor 95 to the detonator 96. If itbe assumed that the switch SS was set to position 1 with the wiperthereof in connection with contact 3 of bank 2 of switch A before themine was launched, a circuit is now closed from negative battery by wayof conductor 69, contact 2 of the extender hydrostat, conductor 74,wiper 2 and terminal 3 of switch A, contact 1 and wiper 94 of switch SS,conductor 95, detonator 96, conductor 67 and relay to operate.

11 thence to positive battery thereby operating the detonator andcausing the mine to explode.

As the switch STP-B operated in response to the first operation of relayD, the Wiper of switch B was moved from the initial or home position toposition 1 thereby closing contact ON-B. The closure of contact ON-Bcompleted a circuit from positive battery, conductor 67, winding ofrelay TD2, conductor 70, wiper 1 and terminal 2 of switch A, conductor87, contact ONB, conductor 74, contact 2 of the extender hydrostat,conductor 69 and thence to negative battery thereby causing the windingof relay TD2 to be energized and the Relay TD2, it will be recalled,does not close its contacts until nine seconds after the relay windinghas been energized. A predetermined delay of nine seconds is thusprovided as contact ON-B closes before the reset magnet RS-B may beoperated to restore the wiper of switch B to its initial position. Inthe case of .a changing magnetic field caused by the passage of a vesselwithin the vicinity of the mine, armature 75 of relay D is repeatedlymoved to circuit closing position by a change in the magnetic fieldimmediately following the release of the reset magnet DR and threeimpulses are thus transmitted by relay P to the stepping magnet STP-B tocause the wiper of switch B to be advance-d to position 3 beforesufficient time has elapsed to allow the wiper thereof to be restored toits normal position by the operation of the reset magnet RSB. In thecase just described of a changing magnetic field caused by a movingvessel in which the switch SS has been set to position 1 wherebyconductor 95 is in circuit with terminal 3 of bank 2 of switch A, theoperation of the stepping magnet STP-A as the wiper of switch B movesinto engagement with terminal 3 of its switch bank, causes a firingcircuit to be closed and the mine to be exploded.

In the event that the ship of curve A has been degaussed before the shipmoved into the vicinity of the mine, the operation of the mine inresponse to the signature of the degaussed ship will best be understoodby reference to curve C of Fig. in which the first operation of relay Dwould take place at a point 97 on the curve C, the second operation atthe point 98 and the third operation at the point 99, at which point themine is exploded. Whereas the point 99 corresponds generally to thepoint 93 of the curve A, by reason of the difierence in configuration ofthe curves A and C as a result of the degaussing process employed, themine may explode at a somewhat different position with respect to theportion of the vessel opposite the mine at the instant of detonation,and in either case the explosion will occur generally amidships.

If it be assumed, by way of example, that switch SS is set to posit-ion2 thereby connecting conductor 95 to terminal 4 of bank 2 of switch A,the detonation of the mine is delayed until wiper 1 of switch A isbrought into engagement with contact 4 of the switch bank. The manner inwhich this is accomplished will now be described.

Shortly after stepping magnet STP-A operates to advance the wipers ofswitch A to position 3, armature 85 of relay TD2 moves into closedposition thereby applying negative battery by way of conductor 86 to oneend of the winding of the reset magnet RS-B and causing the reset magnetto operate and restore the wiper of switch B to its initial or homeposition. When this occurs, the succeeding operation of switch B by asubsequent change in the magnetic field resulting from the continuedmovement of the ship past the mine causes the operation of relay D andthe wiper of switch B to be advanced to position 1. The second operationof relay D by the changing field due to the ships signature causes thewiper to be advanced to position 2, and the third operation causes thewiper of switch B to he stepped ahead to terminal 3 and the wipers ofswitch A to be moved into engagement with their terminals 4. Theengagement of wiper 2 of switch A with terminal 4 of the switch bankcompletes a circuit from negative battery by Way of conductor 69,contact 2, conductor 74, wiper 2 and terminal 4 of switch A, terminal 2and wiper 94 of switch SS, conductor 95, detonator 96, conductor 67 andthence to positive battery, thereby causing the detonator to operate andexplode the mine under the .aft portion of the ship.

In the event that an insufficient portion of the ships signature remainsafter switch B has been restored to normal by the operation of relay TD2to allow relay D to operate a sufiicient number of times to cause thewipers of switch A to be advanced to their terminals 4, the operation ofrelay TD2 in response to the closure of contacts ON-B, at armaturethereof causes the wiper of switch B to be restored to normal withoutagain advancing the wipers of switch A. Thus, by the selective settingof switch SS, any of the terminals 3 to 10 of bank 2 of switch A may beoperatively connected to the detonator 96 whereby the first, second,third, fourth, fifth,

sixth, seventh, or eighth ship passing the mine may be 7 selected atwill for destruction. It will noted that means are provided forpartially arming the mine in response to the operation of the hydrostatand for additionally arming the mine as each additional vessel passesthe mine in succession thereafter. Thus, if the mine firing mechanismwas set to cause the mine to explode as the Nth vessel passes the mine,the mine would be additionally armed as each of the vessels from theN(N1) vessel to the (N-2) vessel moves past the mine and fully armed asthe (N-l) vessel moves past the mine.

When none of the switches T31, T82, and T83 are operated to closedposition, five operations of the switch B arerequired within the timeinterval controlled by relay TD2 to advance the wipers of switch A totheir next succeeding position. Also, if switch TS3 only is closed, fouroperations of switch B are required to advance the wipers of switch A,and when all of the switches T51, T52, and T83 are closed, twooperations of switch B are required to advance the switch A.

Whereas in the illustrative embodiment of the invention shown on Fig. 4,three switches TSl, T S2, and TS3, are employed for changing the numberof operations of the field sensing mechanism required to identify aships signature, it will be understood that additional switches or othermeans may be employed, if desired, for increasing the number of sensingoperations required to identify a ships signature, by merely removingthe strapping between the terminals 5 to 10 of switch B as required andconnecting the additional switches or other means to the terminals 5 to10 in successive order in the manner of the switches TSl to T83.

In the event that the mine is raised from the bed of the body of waterwithin which the mine is laid to a depth sufficient to cause thehydrostat to be forced outward by the spring 18, contact 3 closes andapplies negative battery to the detonator thereby causing the mine toexplode. Also, in the event that contact ON-A fails to open within nineseconds after the extender hydrostat contact 2 is closed, the operationof relay TD2 causes a circuit to be closed from negative battery,conductor 69, contact 2, conductor 74, armature 85 and make contact ofrelay TD2, conductor 86, contact ON-A, conductor 95, detonator 96,conductor 67, and thence to positive battery thereby causing thedetonator to operate and explode the mine.

Self-destruction of the mine is also caused by the failure of switch Bto step to position 2, 3, 4, or 5, as the case may be, within theoperating time of relay TD2 following the closure of contact 2 of theextender hydrostat. Other conditions which may cause theself-destruction of the mine are the failure of relay D to reset, thecontinual operation and resetting of relay D, the failure of relay TD4to operate or the armature 81 thereof to move to open position after therelay has been :operated, or the failure of relay P to operate ortorelease after operation.

Briefly stated in summary, the present invention contemplates theprovision of a mine firing mechanism in which changes in a magneticfield are detected at successive intervals of time and compared with apredetermined interval of time and the firing of the mine is controlledin accordance with the results of such comparison. Furthermore, meansare provided for insuring that the mine will be detonated only by apredetermined number of changing magnetic field conditions detectedsuccessively at intervals during a predetermined interval of time, andin the event that an insufiicient number of changing field conditions isdetected within the predetermined interval of time, the mine is restoredto a detecting condition in which a predetermined number of successivedetection operations must be completed before the mine is detonated.

While the invention has been described with particularity as to onepreferred embodiment of a combination of mechanisms and of each of thevarious elements of the combination, it is to be understood that thishas been done for purposes of disclosure and that various changes andsubstitutions may be readily apparent to those skilled in the art, afterunderstanding the invention herein disclosed, and that the termsemployed in the appended claims are, therefore, to be considered aswords of description rather than of limitation.

The invention herein described and claimed may be manufactured and usedby or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

What is claimed as new and desired to be securedb Letters Patent of theUnited States is: I

1. In a submarine mine of the character disclosed arranged within amagnetic field, a relay, means including said relay for detecting aplurality of changing magnetic conditions within said field, meanscontrolled by said relay for counting signals corresponding to saidchanges of the field detected by said detecting means, means efiectivewhen the first of said conditions has been detected for measuring apredetermined interval of time, and means controlled by said countingmeans for causing said mine to explode when a predetermined number ofchanges in said magnetic field have been counted within saidpredetermined interval of time.

2. In a submarine mine of the character disclosed, an

electrical relay, means including said electrical relay for detectingmagnetic changes in a magnetic field within which the mine is disposed,normally open contact means on said electrical relay adapted to beclosed as the relay operates, a source of electrical power, meansefiective after the mine has been launched for causing the relay to beoperated by said source of electrical power, a slow releasing relayoperatively connected to said contact means, a time delay mechanismcontrolled by said slow releasing relay, means for forcibly restoringand maintaining said contact means in open position during the operationof said time delay mechanism, means controlled by said slow releasingrelay for counting the number of operations of said electrical and slowreleasing relays, and means efiective when a predetermined number ofoperations of said electrical and slow releasing relays have beencounted for preventing an additional closure of the normally opencontact means of said electrical relay by said source of power. 1

3. In a submarine mine of the character disclosed, an electrical relay,means including said electrical relay for detecting magnetic changes ina magnetic field within which the mine is disposed, means adapted to beoperated in time delayed relation to the launching of the mine forpartially arming the mine, and means controlled by said detecting meansin response to a predetermined number of changes in said magnetic fieldfor completely arming the mine.

-tively in response to the number of signal indications counted by saidcounting means, and means effective 4.-In a submarine mine of thecharacter disclosed, means for sensing the movement of a vessel withinthe vicinity of the mine, means controlled by said sensing means forcounting signal indications, each of said signal indicationscorresponding respectively to one of a predetermined number of vesselsmoving past the mine in successive order, means for arming the mineselectively in response to the number of signal indications counted bythe counting means, and means effective when the mine has been armed forcausing the mine to explode opposite the next succeeding vessel passingthe mine.

5. In a submarine mine of the character disclosed, means for sensing themovement of a vessel within the vicinity of themine, means controlled bysaid sensing means for counting a variable number of signal indications,each of said signal indications corresponding respectively to one of aplurality of vessels moving past the mine in successive order, meanssettable at will for setting said counting means to count apredetermined number of signal indications, means for arming the mineselecelectrical relay, means including said electrical relay fordetecting the movement of a vessel within the vicinity of the minearranged adjacent the path of travel of the vessel, means. operated intime delayed relation to the launching of the mine for partially armingthe mine, means for initiating a plurality of cycles of operations ofsaid elec- .trical relay and the. armingmeans, means settable at willfor controlling the number of said cycles of operations of said armingmeans, and. means effective when said cycles of arming operations'havebeen completed for additionally. operating said arming means in responseto the passage of a vessel past-the mine.

7. In a submarine mine of the character disclosed, an electrical relay,means including said electrical relay for detecting themovement of-aivessel within the vicinity of the mine arranged adjacent the path oftravel 'of the vessel, means operated in time delayed relation to thelaunching of themine for initiating a plurality of cycles of operationsof said electrical relay, arming means cyclically controlled by saidelectrical relay, means settable at will for controlling the number ofsaid cycles of operations of said arming means, means efiective whensaid cycles of arming operations have been completed for additionallyoperating said arming means in response to the passage of a vessel pastthe mine, detonating means, means effective when apredetermined numberof vessels vhave passed themine in successive order for causing the mineto be fully armed by said arming means,

and means for causing the mine to be exploded by said detonating meansas the next succeeding vessel moves a past the mine.

controlled by said relay for rendering the detecting means effective todetect magnetic variations in the magnetic field at predeterminedintervals of time, an electrical circuit, a first device for counting apredetermined number of operations of said relay, said first countingdevice ,having means for closing said electrical circuit when apredetermined number of operations of said relay'have 1 been counted, asecond counting device adapted to be operated by said circuit closingmeans, a contact element on said second counting-device and settable toa plurality of difierent positions, a plurality of electrical contactsadapted to be engaged successively by said contact element as saidsecond counting device is set to each of said different positions in,succession, a detonating device,

means settable at will for operatively connecting said detonating deviceselectively to the contacts of said second counting device, and meansfor causingthe mine to be exploded by said detonating means as theselected contact of said second counting device is engaged by saidcontact element.

9. In a submarine mine of the character disclosed arranged within amagnetic field, an electrical relay, means including said electricalrelay for detecting a plurality of changing magnetic conditions withinsaid field, means controlled by said relay for counting signalscorresponding respectively to said changes of the field detected by saiddetecting means, means effective as the first of said signals is countedby said counting means for measuring a predetermined interval of time,and means controlled by said time measuring means for restoring saidcountingmeans -to an initial counting position when less than apredetermined number of changes in said magnetic field have been countedby the counting means within said predetermined interval of time.

10. In a submarine mine of the character disclosed arranged within amagnetic field, a relay, means including said relay for detecting aplurality of uniform groups of changing magnetic conditions within saidfield, means controlled by said relay for counting in succession signalscorresponding respectively to each of said changing conditions detectedby said detecting means, means effective as the first signal of each ofsaid groups is counted by said counting means for measuring apredetermined interval of time, means controlled by said time measuringmeans for restoring said counting means to an initial counting positionafter each of said groups of signals has been counted, anelectro-responsivedevice adapted to count the number of uniform groupsof signals counted by said counting means, and means controlled by saidelectro-responsive device for causing the mine to explode when apredetermined number of uniform groups of changes in said magnetic fieldhave been counted by said electro-responsive device.

11. In a submarine mine of the character disclosed arranged within amagnetic field, a relay, means including said relay for detecting aplurality of uniform groups of changing magnetic conditions within saidfield, means controlled by said relay for counting in succession signalscorresponding respectively to each of said changing conditions detectedby said detecting means, means eifective as the first signal of each ofsaid groups is counted by said counting means for measuring apredetermined interval of time, an electro-responsive device adapted tocount the number of uniform-groups of signals counted by said countingmeans, means controlled by said time measuring means for restoring saidcounting means to an initial counting position after each of said groupsof signals has been counted by saidelectro-responsive device, and meansincluding a device settable at will for causing the mine to explode whena predetermined number of uniform groups of changes in said magneticfield have been counted by said electro-responsive device.

12. In a submarine mine of the character disclosed arranged within amagnetic field, a relay, means including said relay for detecting aplurality of uniform groups of changing magnetic conditions within saidfield, means controlled by said relay for counting in succession signalscorresponding respectively to each of said changing conditions detectedby said detecting means, means effective as the first signal of each ofsaid groups is counted by said counting means for measuring apredetermined interval of time, an clectro-responsive device adapted tocount the number of uniform groups of signals counted by said countingmeans, means controlled by said time measuring means for restoring saidcounting means to an initial counting position after each of said groupsof signals has been countedby said electro-responsive device, meanssettable at will for changingthe number of signals of each group countedby said electro-responsive device, and means including a detonatorcontrolled by said electr'o-responsive device for causing the mine toexplode when a predetermined number of said uniform groups of signalshave been counted by said counting means.

13. In a submarine mine of the character disclosed disposed Within amagnetic field, a relay, means including said relay for detecting insuccession a plurality of changing magnetic conditions within said fieldoccurring during different intervals of time, means controlled by saidrelay for counting in succession signals corresponding respectively toeach of said changing conditions detected by said detecting means withina predetermined interval of time, means eifective when less than apredetermined number of signals are counted by said counting meanswithin said predetermined interval of time for restoring said countingmeans to an initial condition, a detonating device, and means includingsaid detonating device controlled by said counting means for causing themine to explode when said predetermined number of signals are counted insaid counting means.

14. In a submarine mine of the character disclosed disposed within amagnetic field, a relay means including said relay for detecting insuccession a plurality of changing magnetic conditions within said fieldoccurring during different intervals of time, means controlled by saidrelay for counting in succession signals corresponding respectively toeach of said changing conditions detected by said detecting means,within a predetermined interval of time, means eifective when less thana predetermined number of signals are counted by said counting meanswithin said predetermined interval of time for restoring said countingmeans to an initial condition, electro-responsive means adapted to beset by said counting means to different settings when said predeterminednumber of signals are counted in said counting means, a detonatingdevice, and means including said detonating device for causing the mineto explode when said electro-responsive means has been set to apredetermined setting.

15. In a submarine mine of the character disclosed arranged within amagnetic field, mine firing mechanism, means included within said minefiring mechanism for sensing changing magnetic conditions within saidfield during different intervals of time, relay means operativelyconnected to said sensing means and adapted to be operated thereby, asource of electrical power, an electrical circuit, means for closingsaid electrical circuit to cause said relay means to be operatedcyclically by said source of power, a counting device controlled by saidrelay means, said counting device having an initial setting and aplurality of move settings, and means effective when said countingdevice has been moved to a predetermined moved setting for interruptingsaid electrical circuit.

16. In a submarine mine of the character disclosed arranged within amagnetic field, mine firing mechanism, means included Within said minefiring mechanism for sensing changing magnetic conditions Within saidfield during different intervals of time, relay means operativelyconnected to said sensing means and adapted to be operated thereby, asource of electrical power, an electrical circuit, means for closingsaid electrical circuit to cause said relay means to be operatedcyclically by said source of power, a counting device controlled by saidrelay means, said counting device having an initial setting and aplurality of moved settings, means effective when said counting devicehas been moved to a predetermined moved setting for interrupting saidelectrical circuit, detonating means, a device controlled by said relaymeans for measuring an interval of time, and means controlled by saidinterrupting means for causing the mine to be exploded by saiddetonating means when the interrupting means has not been moved to saidpredetermined setting during the interval of time measured by said timemeasuring device.

17. In a submarine mine of the character disclosed arranged Within amagnetic field, a relay, means including d N for detecting changingmagnetic conditions withi 17 I in said field, normally open contacts onsaid relay and adapted to be engaged as the relay operates, a source ofelectrical power, means controlled by the pressure of the body of waterwithin which the mine is laid for causing said relay to be operated bysaid source of electrical power for a predetermined number of cycles ofoperation, means controlled by said relay contacts during said cycles ofoperation for partially arming the mine, and means controlled by saidrelay contacts for additionally arming the mine in response to aplurality of. subsequent changing conditions within said magnetic fielddetected in succession by said detecting means within predeterminedintervals of time.

18. In a submarine mine of the. character disclosed arranged within amagnetic field, a relay, means including said relay for detectingchanging magnetic conditions within said field, normally open contactson saidrelay and adapted to be engaged as the relay operates, a sourceof electrical power, means controlled by the pressure of the body ofwater within which the mine is laidfor causing said relay to be operatedby said source of electrical power for a predetermined number of cyclesof operation, means,

controlled by said relay contacts during said cycles ofop:v eration forpartially arming the mine, means controlled by said relay contacts foradditionally arming the mine in response to a plurality of subsequentchanging condi tions within said magnetic field detected in successionby said detecting means within predeterminedintervalsof time, adetonating device, and means effective when said mine has beenadditionally armed for causing the mine to. be exploded by saiddetonating device in response to a plurality of additional changingconditions within the magnetic field detected in succession by saiddetecting means within an additional predetermined interval of time.

19. In a submarine mine of the character disclosed.

arranged within a magnetic field,,an induction coil for sensing changingmagnetic conditions within said field, a source of electrical power, arelay adapted to be controlled successively by said source of electricalpower and by said induction coil, normally open contacts on said relayadapted to be engaged as the relay operates, an electrical controlconnection between said andthe relay, means responsive to the pressureof the body of water within which the mine is laid for establishing saidelectrical control connection, means efiective when said controlconnection has been established for causing the relay to make apredetermined number of cycles of operation, electro-responsiveswitching means .controlled by said relay contacts for'interrupting saidcontrol connection when said, predetermined number of cycles ofoperation has been completed, and means controlled by said relaycontacts for exploding the mine when a predetermined number of uniformgroups of changing conditions within said magnetic field have beensensed by said induction coil during predetermined intervals of timeafter said control connection has been interrupted.

In a submarine mine'of the character disclosed arranged within amagnetic field, the combination of means including a control relay forsensing magnetic changes Within the field, electrical contacts on saidrelay and adapted to be closed as the relay operates, a source ofelectrical energy, an electro-responsive time measuring device, circuitclosing means controlled by the pressure of the body of water withinwhich the mine is laid for simultaneously initiating the operation ofsaid control relay and the time measuring device, means controlled bysaid relay contacts for causing the relay to make a predetermined numberof cycles of operation within the interval of time measured by said timemeasuring device,

means for counting said cycles of operation, said counting means havingan initial position and a plurality of set positions, a normally opencontact on said counting means adapted to be closed as the countingmeans is moved from said initial position to the first of said pluralityof set source of power 18 positions, switching mechanism adapted to beoperated by said counting means when the counting means has been set toa position corresponding to said predetermined number of cycles ofoperation, means controlled by said time measuring device for restoringsaid counting means to said initial posiction after said switchingmechanism has been operated, and means for transferring the subsequentcontrol of said time measuring means from said circuit closing means tosaid normally open contact on said counting means.

21. In a submarine mine of the character disclosed arranged within amagnetic field, the combination of mine firing mechanism, a detectingcoil included within said mine fin'ng mechanism and adapted to respondto changing magnetic conditions within the field, a relay connected tosaid coil and adapted to be operated thereby, circuit closing meanscontrolled by the pressure of the water within which the mine is laidfor operating said relay, electro-responsive means controlled by saidcircuit closing means for measuring apredetermined interval of time,detonating means, and means for causing the mine to be exploded by saiddetonating means when the relay is not operated within saidpredetermined interval of time.

22. In a submarine mine of the character disclosed arranged within amagnetic field, the combination of mine firingmechanism, a detectingcoil included within said mine firing mechanism and adapted to respondto changing magnetic conditions within the field, a relay connected tosaid coil and adapted to be operated thereby, circuit closing meanscontrolled by the pressure of thewater within which the mine is laid foroperating said relay, electro-responsive means controlled by saidcircuit 1 closing means for measuring a predetermined interval of time,means for resetting said relay after the relay has been operated by saidcircuit closing means, detonating means, and means for causing the mineto be exploded by said detonating means when the relay is not resetwithin said predetermined interval of time.

23. In a submarine mine of the character disclosed arranged within amagnetic field, the combination of mine firing mechanism, a detectingcoil included within said mine firing mechanism and adapted to respondto changing magnetic conditions within the field,"a sensitive relayconnected to said coil and adapted to be operated thereby, circuitclosing means controlled by the pressure of the water within which themine is laid for operating said sensitive relay, electro-responsivemeans controlled by said circuit closing means for measuring apredetermined interval of time.

24. In a submarine mine of the character disclosed arranged within amagnetic field, the combination of mine firing mechanism, a detectingcoil included within said mine firing mechanism and adapted to respondto Chang ing magnetic conditions within the field, a sensitive relayconnected to said coil and adapted to be operated thereby, circuitclosing means controlled by the pressure of the water within which themine is laid for operating said sensitive relay, electro-responsivemeans controlled by said circuit closing means for measuring apredetermined interval of time, a slow releasing relay adapted to beoperated by said sensitive relay, switch stepping mechanism adapted tobe operated by said slow releasing relay -to different settingsincluding a predetermined setting,

detonating means, and means for causing the mine to be exploded by saiddetonating means when the switch stepping mechanism is not operated tosaid predetermined setting within said predetermined interval of time. T

25. In a submarine mine of the character disclosed arranged within amagnetic field, the combination of mine firing mechanism, at detectingcoil included within said mine firing mechanism andadapted to respond tochanging magnetic conditions within the field, a sensitive relayconnected to said coil and adapted to be operatedthereby, circuitclosing means controlled by the pressure of the water within which themine is laid -'for operating said sensitive relay, electro-responsivemeans controlled by said circuit closing "means for measuring apredetermined interval .of time, a slow releasing relay adapted to beoperated "by said sensitive relay, means operated by'said slow releasingrelay for counting the number ofi operations of saidsensitive relay,electro-responsive switching mechanism operatively connected to saidcounting means and adaptedtoxbe moved from an initial position when apredetermined number of operations of sai'd sensitive relay have beencounted, contact means adapted to be disengaged as said switchingmechanism is moved from said initial position, detonating means, andmeans for causing the mine to be exploded by said detonating means whensaid contact means are not disengaged within-said predetermined intervalof time.

26. In a mine firing mechanism disposed within a magnetic field, meansresponsive to a changing magnetic condition of .said field for detectingin succession a plurality of changing conditions of the field within apredetermined interval of time, signal. counting means, and means forselectively voperating said signal counting means in accordance with apredetermined plurality ofchanging conditions of said field detectedbysaid detectingimearis Within, said. predetermined interval of time.

27; In a mine firing mechanism of the character disclosed, a signal;relay, means including said signal-relay responsive to a changingmagnetic fieldfor detecting intime, means controlled by said relay forselecting uniform groups of signals correspondingrespectively 'to apredetermined number of said changing conditions in the field,detonating means, and means controlled by said selecting means forcausing the mine tobe exploded by said detonating means when apredetermined number of said uniform groups of signals has beenselectedbysaid selecting means.

28'. In a mine firingmechanismof the character disclosed arranged.within a magnetic field, a signal relay, means including said signalrelay responsive to a changing magnetic condition within said magneticfield' fordetectinginsuccession. a plurality of subsequent changingmagnetic conditions in the field occurring within a predetermined periodof time, means controlled by said ingmeans toan initial conditionaftersaid groups of] signals have been transferred to said secondaryregistering means. i

29.. In a. submarine mine of the character disclosed arranged within amagnetic field, meansfor detectinga plurality-offs changes in magneticconditionswithin-said field-,- means controlled by said detecting meansfor countingsaid changes, means effective after the first of saidchanges has been counted for resetting said-counting means to an initialposition after a predetermined interval-of time, and means controlledbysaid counting means forcausmgsaidmine to explode when-apredeterminedsplurality of changes in said-magnetic conditions havebeencounted by the counting-means within said predeterminedinterval oftime.

30. In amine firingvmechanism of the-character disclosed, means for:generatinga plurality of'signals inresponse td a. plurality of changingmagnetic conditions associated with a vessel in motion, means controlledby said signals for selecting predetermined groups of the signals,step-.by-step switch means adapted to be moved forward one step-aseachofsaidgrou-ps' of signalsis generated, and means controlled by said switchmeans for causing the mine'to'be fired when a predetermined numberofsteps'has been taken thereby.

31-. In amine firing mechanism of the character disclosed, meansforgenerating-aplurality of signals in response to a plurality ofchanging magnetic conditions associated with a 'vessel in motion, meanscontrolled by said generating means for counting said signals from aninitial signal counting position thereof, means adapted to be renderedeffective to measure a predetermined interval oftime as operation ofsaid counting means is initiated and adapted to restore the countingmeans to said initial position thereof at the end of said interval,step-by-step'switch means adapted to be moved forward one step'undercontrol of said counting means each time a number or signals equal to orgreater than a predetermined-number is counted thereby from said initialposition, and means controlled by said switch means for causing the mineto be fired when a predetermined numben-ofstepshas been taken thereby.

32-. Ina marine mine, in combination, a hydrostat having-apressureresponsive element in communication with the surrounding water, amembersecuredjto said element and adapted to be moved from an initial positionto an extended position, means including said pressure responsiveelementformovingsaid member in either direction to andfromeither one of saidpositions selectively as thehydrostat responds tochanges in pressure ofthe surrounding water, a, first; switch controlled by said member andadapted to be closed thereby when the member is moved from said initialposition, a second switch controlled by said member and adapted to beclosed thereby when; the member is movedfrom said extended position. apredetermined distance, a mine firing circuit including ed to bemovedbetween initial-and extended positions.

thereof as the element responds. to,changes in pressure o f thesurroundingwater, first, second and third switches adapted to beactuated by saidmember, said first switch being closed m mentarily bythe member upon movement thereof from its initial position, said secondswitch being closed by the member upon movement thereoffrom saidinitialposition, said third switch being closed by the member uponpredetermined movement thereof from said extended position, a first minefiring circuit including said, second and third switches and adapted tofire the mine when both the second and third switches are closed and a.second, mine firing circuit adapted to be rendered efiective as thesecondswitch is closed and including a stepper switch adapted to bereset by said first switch.

34, In a marine mine, incombination, a pressure responsive element incommunication-,with the surroundwater, ,a member associated'with saidelement and adapted to-be moved betweeninitial and extended positionsthereof as theelement responds to changes in pressure of thesurroundingwwater, first'and second'switches adaptedto -beactuatedbysaid member, said first switch beingclosed momentarily by the memberupon movementthereof; from its initial jposition, said second switchbeing closed'by the-member upon movement thereof from saidrinitialposition, and a minefi'ring circuit, including means adaptedto be resetto-an initial position thereof by said first-switch,'the'firing circuitbeing armedas saidv second switch is operated.

35. In a marine mine, in combination, a pressure responsive element incommunication with the surrounding water, a member associated with saidelement and adapted to be moved between initial and extended positionsthereof as the element responds to changes in pressure of the water, amine firing circuit, and means including a pair of switches actuated bysaid member in predetermined sequential order and effective as saidmember moves from said initial position for causing said firing circuitto be first reset to an initial condition thereof, and thereafter set inan armed condition.

36. In a marine mine, the combination of a hydrostatic device includinga member adapted to be moved between initial and extended positions inresponse to variations in pressure of the surrounding water caused bychanges in the depth of submergence of the mine, three switchesconstructed and arranged for operation by said member in sequentialorder in response to a predetermined movement of the member between saidpositions as the mine 22 is lowered and thereafter raised within thewater, a resettable mine firing circuit, and means including saidswitches for resetting, arming, and firing said firing cir' cuit in theorder named during said predetermined movement of the member.

References Cited in the file of this patent UNITED STATES PATENTS1,382,374 Maxim June 21, 1921 1,390,768 Dorsey Sept. 13, 1921 1,538,316Duffie May 19, 1925 1,766,524 Loftin June 24, 1930 2,066,211 McCrearyDec. 29, 1936 FOREIGN PATENTS 803,907 France July 20, 1936 836,663France Oct. 17, 1938

